1. Technical Field
The present disclosure relates to a semiconductor device and a method for fabricating the same.
2. Description of the Related Art
Semiconductor devices are utilized in a variety of industrial fields such as electronic equipment, automobiles and/or ships due to advantages such as light weight, small size and/or low cost. A field effect transistor (hereinafter, referred to as “transistor”) is one of essential single elements constituting a semiconductor device. Typically, the transistor may include a source and a drain formed to be spaced apart from each other on a semiconductor substrate and a gate electrode covering the top of a channel region between the source and the drain. The source and the drain may be formed by injecting dopant ions onto the semiconductor substrate, and the gate electrode may be insulated from the channel region via the gate oxide film interposed between the semiconductor substrate and the gate electrode.
The above described form of transistor is widely used as a single element constituting a logic circuit and/or a switching device in the semiconductor device. In the rapidly developing electronics industry, demand for a high speed, high reliability and a multi-functional ability has been increasing for semiconductor devices. In order to meet this demand, the structure of semiconductor devices has been getting more complex and the size of the transistors has been highly miniaturized. Accordingly, transistors may decrease in turn-on current. The decrease in turn-on current may cause deterioration in operation speed of transistors. For these reasons, regarding the fabrication of high-integrated semiconductor devices, research has been undertaken on methods to increase mobility of carriers in channels for improvement of performance of the semiconductor devices. Attempts have been made to increase mobility of electrons or holes by application of tensile stress or compressive stress to channel regions of transistors to improve driving current characteristics and operation speed of the transistors. For example, in case of n-channel metal oxide semiconductor (NMOS) transistors, tensile stress may be applied to channel regions between the source and the drain, whereas in case of p-channel metal oxide semiconductor (PMOS) transistors, compressive stress may be applied thereto.
For this purpose, trench regions should be formed in the source and drain regions and a material having a less or greater lattice constant than that of silicon (Si) should be formed to enable application of stress between the source and drain regions. In this case, electrical properties may be changed according to depths of the trenches and sizes of thin films, and thus disadvantageously causing deterioration in yield.